The following includes information that may be useful in understanding the present teachings. It is not an admission that any of the information provided herein is prior art, or material, to the presently described or claimed inventions, or that any publication or document that is specifically or implicitly referenced is prior art.
1. Field of the Invention
The present teachings relate to, but are not limited to, the field of corn product production. The invention relates, for example, to de-oiled flour and production of methane, ammonia, and modified dried distillers grains as well as modified dry grind ethanol processes for their production.
2. Description of the Background Art
Corn oil has a number of properties and uses that are attractive to consumers and to producers of consumer products. Refined corn oil is crude corn oil from which fatty acids and phospholipids have been removed. Refined corn oil is reputed to have excellent frying quality and resist smoking and/or discoloration. Refined corn oil typically has a pleasant taste, resists development of off-flavors, and has a high polyunsaturated fat content. Refined corn oil has also been postulated to reduce blood cholesterol levels. Products such as margarines, salad oils, and cooking oils may include refined corn oil. Corn oil may also be used for biodiesel applications.
Corn processing methods may be divided into a number of broad groups, including dry grind ethanol, modified dry grind ethanol, corn wet milling and corn dry milling (Singh, V., et al., “Modified Dry Grind Ethanol Process,” Publication of the Agricultural Engineering Dept. of Univ. of Ill. and Urbana-Champaign, UILU No. 2001-7021, Jul. 18, 2001, incorporated by reference herein). Variation within processes may occur based on the preferences of the miller.
In a typical traditional dry grind ethanol operation, whole corn is ground, treated with enzymes, and cooked. The resulting “mash” is treated with enzymes to further liberate glucose from the starchy endosperm tissue. The converted mash is fermented and distilled, producing ethanol, carbon dioxide, and distillers dried grains (DDGs), which are the undissolved solid components (stillage) remaining in the fermentation tank after the broth is removed. These conventional DDGs are thus comprised of yeast and unfermented left over components of the corn.
Traditional dry grind ethanol operations have a number of disadvantages. For instance, use of the entire kernel in the mash, including the non-starch portions of the kernel, reduces the efficiency of the operation. Furthermore, the non-ethanol byproducts (including DDGs) have a relatively low value, and they include a high oil content that is relatively difficult to remove. A typical conventional dry grind ethanol operation is depicted in FIG. 1.
In a typical modified dry grind ethanol operation, corn is first cleaned in a dry state, to remove cobs and other undesirable components, such as iron or stones. The corn may also be wet-cleaned to remove dirt or dust. Following cleaning, the corn is tempered to between about 14% and 22% moisture, typically about 20% moisture. Tempering entails treating the corn with cold water, hot water, and/or steam. This softens the bran and germ and allows them to be more easily separated from the endosperm.
Following tempering, and while the corn is still moist, the germ, tip cap, and pericarp (bran) are separated from the endosperm, which is customarily used to make grits, meals, and flours. The bran and germ proceed through the “through stock” stream, which is dried, cooked, and aspirated. This removes the bran. The remaining dried germ, which typically contains about 45% corn oil on a dry basis, is transferred to a separate facility, where the oil is removed through chemical extraction or auger press/expeller. The corn residue from the press or extraction (oil cake) is then used as an animal feed.
The non-bran, non-germ components of the kernel (principally endosperm tissue) are ground and converted to mash, as is done in the conventional dry grind ethanol operation. Again, the mash is typically treated with enzymes to liberate glucose. The mash (more accurately the glucose in the mash) is fermented and distilled, producing ethanol, DDGs and carbon dioxide. Because the germ, which contains the highest oil content of the corn grain is not used in the fermentation process, the DDGs from this modified process may be considered de-oiled relative to the DDG's obtained from the ordinary process A typical modified dry grind ethanol process is shown in FIG. 2.
Modified dry grind ethanol operations are typically more advantageous than conventional dry grind ethanol operations, because the additional capital cost involved in establishing modified operations is offset by the added value obtained by separating the germ and bran from the materials used in fermentations. The separated germ may be shipped to a treatment facility, then extracted or treated with an expeller to obtain corn oil and the remaining oil cake is customarily used as an animal feed component.
Corn dry milling, without ethanol production, typically involves addition of water to the corn kernel, increasing the moisture content to about 22%. Germ is made more resilient by the addition of water due to differential swelling relative to the other kernel components. The corn is treated (by abrasion or grinding) to break the kernel into bran, germ, and endosperm fragments, and the pericarp and germ fragments are removed from the endosperm. Because the separation is not highly specific, the germ fraction from corn dry milling includes a lower corn oil concentration than the germ fraction from a modified dry grind ethanol operation. Therefore, the germ and bran fractions are usually sold as ingredients in animal foods. The germ and bran fractions are typically not incorporated into any whole corn products, because the amount of oil that is present may be sufficient to foul the product. Following removal of the germ fraction and the bran fraction, the endosperm fraction is separated based on size of the various flakes Endosperm products include flaking grits, brewers grits, cones, meal, and flour. A typical dry corn milling process is shown in FIG. 3.
It would be desirable to provide an improved dry corn milling process to extract further value from corn and similar grains. It would further be desirable to produce an improved de-oiled DDGs and other de-oiled whole grain products that may be made from such an improved process.